1. Field of the Invention
The present invention relates to a method of formatting and encoding, and more particularly, to a method of formatting and encoding uplink control information in a wireless communication system.
2. Discussion of the Related Art
With the growing demand for transmission of data in an uplink direction, various methods of transmitting data using a high speed transmission channel are being discussed. In particular, an Enhanced Uplink Dedicated Channel (E-DCH) is a prime example of such high speed transmission channel in a 3rd Generation Partnership Project (3GPP) wireless mobile communication system.
Compared to the existing Dedicated Channel (DCH), the new E-DCH boasts, among other functions, a Hybrid Automatic ReQuest (HARQ). In HARQ, a base station (Node B) receives a data packet transmitted from a user equipment (UE) and performs decoding operation to determine whether there is any error in the received data packet. If there is no error in the data packet (successfully decoded), Node B transmits an Acknowledgment (ACK) signal to the UE. On the other hand, if there is error in the data packet (unsuccessfully decoded), Node B transmits Negative Acknowledgment (NACK) signal to the UE. The UE then transmits a new data packet upon receipt of ACK or retransmits the same data packet upon receipt of NACK.
Another feature of the E-DCH relates to Node B determining statuses of UEs and scheduling transmission of data packets from a UE to Node B at every Transmit Time Interval (TTI). Through scheduling of data packet transmissions, uplink transmission capabilities of the E-DCH can be further enhanced from that of the DCH. It is important to note that Node B must have the status information of each UE in order to successfully execute scheduling operation. In practice, each UE can provide its information via a periodic transmission or non-periodically when significant change or update occurs to scheduling information.
For scheduling of data packet transmissions, Node B must have certain information, namely, a buffer status of each UE and transmission power status, among others. For example, as related to the buffer status, Node B has to have information on how much data is stored in the buffer as well as how much additional data can be stored in the buffer. As for the transmission power status, for example, Node B has to know the amount of transmission power remaining in the UE (or how much transmission power can be assigned to the E-DCH).
As is the operation in DCH, the E-DCH transmits data and format information separately. Here, control information is information regarding what method was used to format the E-DCH and how the formatted E-DCH was transmitted. The information is used to accurately decode the data. Examples of format information include an E-DCH Transport Format Combination Indicator (E-TFCI) which shows how the data is actually formatted, and a redundancy version for the HARQ and a sequence number.
In transmitting the control information, the transmission can easily contain transmission errors. The transmission errors include incorrectly determining occurrence of transmission when no transmission has been made, and vice versa, for example. Such transmission errors cause inefficiency to the operation of the resources in the wireless communication system. It is the objective of the present invention to introduce a more efficient means of encoding and transmitting of control signal, in turn reducing errors caused in transmission.
To combat errors occurring in transmission, a threshold detection method has been used. In the threshold detection method, an energy level of the corresponding interval is detected. From the detection, if it is determined that the energy level, which significantly exceeds the threshold level, has been transmitted, only then does Node B determine that a signal has been transmitted.
Unfortunately, this threshold detection method is not without errors. To put differently, even if a transmission has been completed, the method can incorrectly determine that the transmission has not been made. This incorrect determination could be a result of a very low energy level input from the transmitting end due to a low signal transmission affected by poor channel status. In addition, even if there is no transmission, the method can erroneously determine that a transmission has taken place as a result of large interference.
As one of possible solutions to errors in the threshold detection method, an error detection method can be employed. Generally, the error detection code is applied or attached to the short information. However, the short information combined with the error detection code has varying lengths.
A block code is advantageous is encoding short information. That is, the block code is good for encoding information being short in length. However, a problem with a block encoder is that the block encoder can only encode information bits having fixed lengths. In other words, the block encoder can only encode fixed number of information bits. Therefore, the block encode cannot encode a plurality of information bits having different lengths. In order to encode information bits having different lengths, independent block encoders which correspond to each different length is required. Here, each block encoder is only able to encode a short information bit having a specified length that corresponds to the length of the block encoder. Consequently, a number of block encoders that is able to encode short information bits having different lengths can be too numerous, resulting in ineffective and inefficient block encoders.